Production of copolymers



United States rnonucrroN on COPOLYMERS Alfred L. Miller, Roselle, N. 3.,assignor to Celanese Corporation of America, New York, N. Y., acorporation of Delaware No Drawing. Application lune 5, 1952, Serial No.291,975

1 Qiaim. (Cl. 260-355) This invention relates to the production ofpolymers and relates more particularly to a novel process for theproduction of polymers by the copolymerization of acrylonitrile and ancc,fi-1II1S3.tllI8.t6d acid amide.

An important object of this invention is to provide a novel process forthe production of polymers by the copolymerization of acrylonitrile andan a,,8-UHS3H11'2116C1 acid amide which will be eihcient and inexpensiveand which will yield products having a high intrinsic viscosity.

A further object of this invention is to provide a process for theproduction of polymers by the copolymerization of acrylonitrile and anone-unsaturated acid amide in an aqueous medium containing awater-miscible organic solvent.

Other objects of this invention will be apparent from the followingdetailed description and claim.

According to the present invention, polymers are produced bycopolymerizing acrylonitrile and an c b-unsaturated acid amide in anaqueous medium containing a water-miscible organic solvent. The polymersobtained in this manner have a high intrinsic viscosity and are wellsuited for a wide variety of applications. Depending upon their precisecomposition, they are soluble in readily available, inexpensivesolvents, forming solutions which may be employed for the production offilamentary materials, films and the like, for example, by dry-spinningor wetspinning processes. The polymers have a good afiinity for and arereadily dyed by a large number of commercially available dyestufis. inaddition, their melting point is relatively high so that they aresuitable for use in textiles and the like.

In carrying out the polymerization, the concentration of thewater-miscible organic solvent is kept at a low value to obtain productshaving the highest intrinsic viscosity. Advantageously, theconcentration of watermiscible organic solvent in the aqueouspolymerization medium is maintained at a value between the minimum whichwill dissolve all the monomers to form a homogeneous solution and aconcentration of about 60 percent by volume or preferably about 35percent by volume. When lower concentrations of water-miscible organicsolvent are present, all of the monomers do not dissolve and thepolymerization may not go to completion, or, if it does go tocompletion, will produce a more heterogenous product. On the other hand,when higher concentrations of water-miscible solvent are employed, theintrinsic viscosity of the polymers is reduced. The extent of suchreduction in viscosity will depend, to some extent, on the nature of thewater-miscible organic solvent as pointed out more fully below.

Suitable water-miscible organic solvents that may be employed to formthe polymerization medium include, for example, the low molecular weightalcohols, such as methanol, ethanol, N-propanol, iso-propanol,N-butanol, iso-butanol and tertiary-butanol. There is some tendency forthe alcohols to act as chain transfer agents interrupting the growth ofthe polymer chain. The low concentration of alcohol employed in thepolymerization medium 2,741,652 Patented Apr. 10, 1956 keeps this efiectto a minimum and permits the production of polymers of high intrinsicviscosity. In addition, it has been found that by employing secondary orpreferably tertiary alcohols this effect may be reduced even further topermit the production of polymers of extremely high intrinsic viscosity.The presence of a water-miscible organic solvent permits thepolymerization to be carried out with higher concentrations of monomersso that a larger quantity of polymer may be produced in a reactionvessel of given volume. Monomer-solvent ratios that have been foundsuitable for the production of polymers of high intrinsic viscosityrange from about 25 to 100 grams of monomer per liter of solvent.

Examples of suitable 0:, 3-11I1S3U1I21l6d acid amides, that may becopolymerized with acrylonitrile according to the process of the presentinvention, include N-methyl acrylamide, N-ethyl acrylamide, N-propylacrylamide, N-butyl acrylamide, N-octyl acrylamide and the like,N-nhenyl acrylamide and the corresponding methacryl- A particularlyvaluable class of a,fi-unsaturated '25 that may be copolyrnerized withacrylonitrile are those in which the nitrogen atom carries a substituentlinked thereto by a tertiary carbon atom or by a secondary carbon atomforming part of a cycloalkyl group as described in application 3. No.164,855, filed May 27, 1950. Examples of a,fi-unsaturated acid amidesfalling Within this class are ii -tertiary butyl acrylamide, N-tertiaryamyl acrylamide, N (dimethyl phenyl carbinyl) acrylamide, N-cyclohexylacrylamide, N-cyclopentyl acrylarnide and the correspondingmethacrylamides, N-tertiary butyl crotonamide, N-tertiary butylcinnamamide, N- tertiary amyl crotonamide, N-cyclohexyl cinnamamide,N-cyclopentyl crotonamide and N-cyclopentyl cinnamarnide.

The percentage of acrylonitrile in the polymer will vary depending uponthe properties it is desired to obtain in the final product. Generally,good result are obtained when the monomer mixture contains at leastabout 5 percent by wei ht of acrylonitrile, or, preferably, betweenabout 10 and 90 percent by wei ht of acrylonitrile. This will yieldpolymers having a lower percentage of acrylonitrile because the0:,[3-11I1S2tl11'21t6d acid amide apparently polymerizes at a somewhatfaster rate than the acrylonitrile.

The polymerization may be carried out at temperatures of between about20 and C., or even at temperatures below 0 C., and will usually becompleted in between about 1 and 6 hours. In addition to the monomers,the polymerization medium will contain catalysts, initiators and thelike, all as Well known in the art. Suitable catalysts, which may bepresent in concentrations of between about 0.5 and 3% by weight based onthe total weight of the monomer, include, for example, potassiumpersulfate, ammonium persulfate and benzoyl peroxide. Suitableinitiators, which may be present in concentrations of between about 0.1and 1.5% by weight based on the total weight of the monomer include, forexample, sodium metabisulfite, and iron salts.

The following examples are given to illustrate this invention further.

Example I into a vessel equipped with a stirrer, there are charged 465parts by weight of aqueous methanol, 20 parts by weight of acrylonitrileand 5 parts by weight of N-cyclohexylacrylamide, and the vessel ispurged with nitrogen. The temperature is raised to 45 C. and there isthen introduced into the vessel aqueous solutions containing 0.5 part byWeight of potassium persulfate in 25 parts by weight of water and 0.25part by weight of sodium metabisulfite in 10 parts by weight of water.The original concentration of the methanol is such that after theaddition of the water the methanol concentration is 25% by 'nitrileas'determined by nitrogen analysis.

- nitrogen analysis. The polymer has anintrinsic viscosity 7 of 1.45in'dimethylformamide.

When the polymerization is repeated in 50% by volume aqueous methanol,the yield of polymer drops to 54% of theory and the polymer has anintrinsic viscosity of only 0.57.

Example II Into a vessel equipped with a stirrer, there are charged 950parts by Weight of aqueous tertiary butanol, 32 parts by Weight ofacrylonitrile and 8 parts by weight of N-cyclohexylacrylamide, and thevessel is purged with nitrogen. The temperature is raised to 45 C. andthere is then introduced into the vessel aqueous solutions containing1.0 part by weight of potassium persulfate in 25 parts by weight ofwater and 0.5 part byweight of sodium metabisulfite in 25 parts byweight of water. The original concentrationof the tertiary butanol issuch that after the addition of the water, the tertiary butanol,concentration is 30% by volume.- The solution is stirred for 20 hoursand the polymer which precipitates out of the polymerization medium isrecovered, washed and dried. There is obtained a polymer containing 74%by weight of acrylo- The polymer has an intrinsic viscosity of 1.45 indimethylformamide.

When the polymerization is repeated in 50% by volume aqueoustertiary-butanol, the polymer has an intrinsic viscosity of only 0.68.

Example III Into a vessel equipped with a stirrer, there are charged ata temperature of 27 0., 13,400 parts by weight of aqueous methanol,containing 25.4% by volume of methanol, 175 parts by weight ofacrylonitrile and 325 parts by weight of N-tertiary butyl acrylamide,and the vessel is purged with nitrogen. There is then introduced It isto be understood that the foregoing detailed description is given merelyby way of illustration and that many variations may be made thereinwithout departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patentis: p A process for the production of polymers which comprisescopolymerizing in 30% by volume aqueous tertiary butanol 32 parts byweight of acrylonitrile and 8 parts by Weight N-cyclohexylacrylamide inthe presence of 1 part by weight of potassium persulfate and 0.5 part byweight of sodium metabisulfite for a period of '20 hours at atemperature of C.

References Cited inthe meet this patent UNITED STATES PATENTS 2,456,360Arnold Dec. 14, 1948 2,546,220 Fryling Mar. 27, 1951 2,560,680 AlleweltJuly 17, 1951 2,566,821 Brown et al. Sept. 4, 1951 2,567,109 HowardSept. 4, 1951 2,587,465 et al. Feb. 26, 1952

